The 18-year-old fashion student who collapsed in a Midtown subway station and died – supposedly after her boyfriend pushed her minutes earlier – appears actually to have succumbed to a rare but deadly side effect of a birth-control device, cops said yesterday.

Based on new information from the medical examiner’s office, probers now believe that Zakiya Kennedy formed blood clots as the result of using the “patch” contraceptive – and that one of the fatal clots eventually moved into her lung and killed her, law-enforcement sources said.

The sources said the girl had switched from using the more common birth-control pill to the patch about three weeks ago.

Both the FDA and the patch’s manufacturer have warned that the contraceptive, like the pill, carries the risk of forming potentially deadly clots.

The bizarre case first began when Kennedy, a stunning aspiring model from the Upper West Side, walked up to a cop on the platform in the 42nd Street station just after 8 p.m. Friday, told him she had just fallen, and complained of excruciating pain in her head and leg, police said.

She then collapsed. She was taken to Bellevue Hospital, where she died about an hour later.

Kennedy’s family has contended that the teen had been pushed down a flight of subway steps by her high-school sweetheart during a heated argument the pair had minutes earlier.

Kennedy had been angry over the fact that her boyfriend had failed to get her tickets to the upcoming Beyoncé concert at the Garden, and when she confronted him, he shoved her, the family said. That fall left her with a banged head and ultimately contributed to her death, they claimed.

Yesterday’s news of a shift in the apparent blame for her death – to her use of the contraceptive – did little to soothe the anger that Kennedy’s family still harbors against her beau.

While the boyfriend left moments after the alleged shoving incident – possibly not even aware that Kennedy had fallen – the girl’s grieving father said he still bore blame.

“He [the boyfriend] said they got into an argument and it escalated and he pushed her,” said the teen’s dad, Kevin Kennedy.